Tailored blank

ABSTRACT

A tailored blank is provided by welding a pair of constituent parts to one another in juxtaposition. The parts are laser welded together to form a unitary blank that is subsequently formed into a shaped finished component.

This application is the national phase of international applicationPCT/CA97/00854 filed Nov. 13, 1997 which designated the U.S.

FIELD OF INVENTION

The present invention relates to a method of forming tailored blanks tobe used to produce shaped metal components.

BACKGROUND OF THE PRIOR ART

Sheet metal components of complex shapes are typically produced from aplanar blank that is formed into the finished shape through a series offorming or stamping operations. Where relatively complex components areto be produced, it is usual to build the component out of a number ofindividual elements, each of which is stamped from a blank. The need touse multiple components may result from the complexity of the finishedproduct or may result from the different characteristics of the materialrequired in different areas of the component. For example, if thecomponent is a door frame of an automobile, the majority of the doorframe may be formed from a relatively thin metal sheet but the mountingpoints for the hinges of the door require extra strength. The use ofmultiple elements to produce the finished component increases themanufacturing complexity.

To mitigate this complexity, it has been proposed to produce a tailoredblank in which appropriately shaped sheets of material are connectededge to edge by a laser welding process to produce a unitary blank. Whenformed, the blank produces a component with differing materialcharacteristics through the structure. This process permits optimum useof the material but at the same time minimizes the subsequent assemblyof multiple elements into the final component.

The production of a tailored blank requires the constituent sheet metalparts to be cut accurately so that the laser welding may be performedefficiently and retain an adequate weld quality. This requires precisioncutting of the constituent components and in our published ApplicationNos. 9624039.5 filed Nov. 19, 1996, 9624652.5 filed Nov. 27, 1996 andApplication No. 9700251.3 filed Jan. 8, 1997, each of which were filedin Great Britain and are abandoned, various methods are described tomitigate the difficulties encountered with obtaining the requiredprecision from the constituent parts. However, in certain circumstances,it is desirable to produce a formed component with a very high qualitysurface finish so that subsequent processing such as painting can beaccomplished with a minimum of refurbishment of the surface afterwelding. While laser welding offers in general a relatively high-qualitywelded surface and the processes contemplated in the above-mentionedapplications further facilitate the production of a smooth outersurface, there is nevertheless the need for a tailored blank that may beused directly to produce a finished surface.

It is therefore an object of the present invention to obviate ormitigate the above disadvantages.

SUMMARY OF THE INVENTION

In general terms, the present invention provides a tailored blank havinga pair of sheet metal constituent parts each having a pair of oppositelydirected major surfaces. A major surface of one of the components isplaced on the major surface of another of the components and the partswelded to one another to produce a unitary blank. The blank may then besubsequently formed into a component of varying materialcharacteristics.

Preferably the welding of the constituent parts is performed by laserwelding and as a further preference, the laser welding does notpenetrate to the other major surface of the other constituent part.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described by way of exampleonly, with reference to the accompanying drawings in which

FIG. 1 is a sectional view of a pair of constituent parts prior toprocessing;

FIG. 2 is a sectional view of the components after processing;

FIG. 3 is a top perspective view of the components after processing;

FIG. 4 is a schematic representation of a part formed from thecomponents of FIG. 3;

FIG. 5 is an alternative embodiment of tailored blank;

FIG. 6 is a further embodiment of a tailored blank;

FIG. 7 is a sectional view of an alternative processing arrangement of atailored blank;

FIG. 8 is a sectional view showing the processing of tubular components;

FIG. 9 is a perspective view of a finished component formed from theblank of FIG. 8;

FIG. 10 is a side view of a further embodiment of blank similar to FIG.9;

FIG. 11 is a side view of a yet further embodiment similar to FIG. 10;

FIG. 12 is a section of an alternative arrangement of blankincorporating a supplementary component;

FIG. 13 is a plan view of a blank used in the forming of an automobilecomponent;

FIG. 14 is a section on the line 14—14 of FIG. 13;

FIG. 15 is a section similar to FIG. 14 showing a subsequent step in theforming;

FIG. 16 is a sectional view of the finished component;

FIG. 17 is a flow chart showing the sequence of steps performed in FIGS.13-16;

FIG. 18 is an exploded view of components of a further embodiment ofblank;

FIG. 19 is a side view of the assembled blank of FIG. 18;

FIG. 20 is a plan view of FIG. 19;

FIG. 21 is a section of a further embodiment of the blank shown in FIG.19; and

FIG. 22 is a series of schematic representations of blanks formed usingthe embodiments of FIGS. 18-21.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring therefore to FIG. 1, a pair of constituent parts 10,20 whichmay have differing characteristics—in this case differingthicknesses—are each planar and formed from weldable sheet metal. Assuch, each has a pair of oppositely directed major surfaces 12,14 and22,24 interconnected at the periphery by edges 16,26 respectively.

The constituent parts 10,20 are positioned in juxtaposition with onemajor surface 14 of the constituent part 10 overlying and in abutmentwith one of the major surfaces 22 of the constituent part 20. Theconstituent part 10, which is of smaller area than that of theconstituent part 20, is positioned within the periphery of part 20 suchthat after forming, an increased thickness of material will be availablein the desired region of the finished component.

The constituent parts 10,20 are secured in abutting relationship byclamps 32 of suitable form including magnetic clamps if the componentsthemselves are magnetic. A laser 34 directs a beam 36 onto the exposedmajor surface 12 of the constituent part 10 and produces local meltingof the constituent part 10 and the major surface 22. The beam 36 iscontrolled so that partial penetration of the component 20 is obtainedbut the liquid region 38 does not extend to the lower surface 24. Theirradiated area may be shielded with an inert gas in a conventionalmanner as appropriate.

The beam 36 is caused to translate relative to the constituent parts10,12 along a predetermined path so that as the beam 36 moves, theconstituent part 10 and part of the constituent part 20 melt locally inthe region indicated by numeral 38. Continued movement of the beam 36allows the region 38 of the constituent parts 10,20 to solidify afterpassage of the beam and be joined to one another as indicated by weld40.

As indicated in FIG. 3, the beam 36 is repositioned laterally to providewelds at spaced locations and thereby secure the one constituent part 10to the other constituent part 20. Alternatively, multiple beams may beused to produce welds simultaneously.

After welding, the constituent parts 10,20 provide a unitary tailoredblank 42 which may then be subsequently formed into a component of therequired shape as shown schematically in FIG. 4. A pair of complementarydies 44,46 engage opposite faces 12,24 of the blank 42 to form it into ashape defined by the dies. The components 10,20 are each formedresulting in a finished component of the desired complex shape.

By controlling the beam 36 such that melting only proceeds part waythrough the constituent part 20, the major surface 24 is not adverselyaffected by the welding process and therefore presents a continuoussmooth surface that may not require additional processing prior tofinishing. At the same time, the blank provides varying materialcharacteristics in the finished component. It will be appreciated thatfull penetration of the constituent part 20 may be permitted where finalsurface finish is not significant.

In tests conducted with the composite blank 42 shown in FIG. 3, thefollowing parameters were utilized:

relative speed between laser beam and the constituent part: 6.2 metersper minute

laser beam power: 6 kilowatts utilizing a CO₂ continuous laser;

laser beam mode: TEM₀₁

laser beam diameter: 0.028 inches

shield gas: helium above, argon below;

thickness of constituent part 20: t¹=0.034 inches;

thickness of constituent part 10: t²=0.074 inches;

constituent part material: galvaneal (hot rolled galvanized mild steel)

Naturally the constituent parts may be similar to one another having thesame thickness and composition or may be selected with differentcharacteristics, such as thickness, composition, coating or the like. Byselecting the constituent part 10 of the appropriate characteristics,the unitary blank 42 is formed with a uniform surface but with localreinforcements to provide varying characteristics in the formedcomponent. In one particularly beneficial embodiment, the constituentpart 20 is zinc coated and the constituent part 10 is cold rolled steel.The surface 24 of the part 20 is thus not affected by welding to providea continuous zinc coated surface that may be used as an exterior paintsurface and/or for corrosion resistance.

Alternative arrangements of constituent parts and welding may beutilized to produce the required tailored blank. For example, as shownin FIG. 5, the constituent part 10 a is secured to the constituent part12 a through intersecting lines of welds 40 a indicated so that theconstituent part 10 a is secured about its entire periphery to theconstituent part 12.

As shown in FIG. 6, the constituent part 10 b need not be rectangular oreven of regular shape, and the laser beam 36 b may be moved along a pathconforming to the periphery of the constituent part 10 b to secure it toa differently-shaped constituent part 20 b.

The above embodiments contemplate the welding of the constituent part ata location spaced from the periphery of the constituent part 10 a.However, as indicated at FIG. 7, the constituent part 10 c may be weldedto the constituent part 12 c by following the edge of the constituentpart and providing a lap weld 40 c along the periphery of theconstituent part 10 c. Again, where the major surface 24 c is to be usedas a finished surface, the beam 36 c is controlled to limit penetrationthrough the constituent part 20 c.

The above embodiments show the formation of tailored blanks fromgenerally planar constituent parts. However, as indicated in FIGS. 8-11,tubular constituent parts 10 d,20 d may be utilized to provide localreinforcement in the walls of a tubular blank. As seen in FIG. 8, theconstituent part 10 d is tubular and located within tubular component 20d. Laser beam 36 d impinges on the radially outwardly-directed majorsurface 12 d and penetrates to the abutting major surfaces 14 d,22 d toweld the two surfaces together. The tubular constituent part 20 d may berotated about its longitudinal axis relative to the beam 36 d to producea circumferential weld.

The constituent parts 10 d,20 d may of course be connected atlongitudinally spaced locations to connect the constituent parts asrequired for subsequent forming.

This arrangement is particularly useful where the tubular blank 42 d isto be used in a hydroforming operation where high pressure fluid is usedto expand a tubular blank 42 d into a die cavity. An example is shown inFIG. 9 where a radial expansion of the tubular blank 42 d produces abulbous frame component with varying wall thickness. The localreinforcement provided by the part 20 d permits varying characteristicsto be obtained along the length of the finished component.

As shown in FIG. 10, the constituent part 20 e may be providedexternally of the tube 10 e and at a number of longitudinally spacedlocations. This facilitates placement of the parts 20 e and permitstailoring of the tubular blank 42 e. When used in vehicle frames, thevariation of wall thickness provided by constituent parts 10 e,20 epermits a progressive crush resistance to be obtained for the finishedcomponent. Similarly, as illustrated in FIG. 11, multiple constituentparts may be stacked on top of one another to provide further variationin wall thickness. Of course, a similar stacking may be accomplishedwith planar components illustrated in FIGS. 1-7.

The lamination of the tailored blank 42 also enables supplementarymaterials to be incorporated into the blank 42. As shown in FIG. 12, thesound transmission characteristics may be modified by incorporating anon-metal layer 48, such as plastic or paper, between the constituentparts 10 g,20 g. Typically, the intermediate layer 48 may be 0.004inches thick and lies within the smaller constituent part 10 g toseparate the major surfaces 14 g,22 g and provide a peripheral margin 50in which contact between the surfaces 14 g,22 g is not inhibited. Theconstituent parts may be seam welded around the peripheral margin 50 toinhibit moisture ingress or intermittently welded to retain the layer48. The resultant tailored blank 42 g may then be formed to the requiredshape in a press with the intermediate layer 48 retained in situ duringforming.

A further example of a component formed from a tailored blank is shownin FIGS. 13-16 where the formation of a shock tower for use in a vehiclebody is shown using the process steps shown in FIG. 17. A shock tower isused to support suspension components in a vehicle and as such issubjected to severe local shear loadings. However, the shock tower isusually elongated to accommodate the vertical displacement of suspensioncomponents and therefore has a significant wall area.

A blank 42 h is formed from a constituent part 20 h and a pair of firstconstituent parts 10 h. The second constituent part 20 h is formed froma planar sheet of cold rolled steel with a pair of D-shaped cutouts 52located in local depressions 53. The cutouts 52 and depressions 53 areprovided in a preforming step by stamping a sheet of material in aconventional manner.

The first constituent parts 10 h are cut from sheet stock which isthicker and of higher strength to serve as a mounting point and locatedover the cutouts 52. The parts 10 h overlap the edges of the cutouts 52within the depression to provide a peripheral margin 54 of juxtaposedparts. The depth of the depressions corresponds to the thickness of theparts 10 h so that the major surfaces 24 h and 14 h are coplanar. A flatsurface is thus provided to facilitate subsequent forming operations.

The constituent parts 10 h,20 h are then laser welded to one another inthe margin 54 with a continuous weld 40 h as indicated above.

The resultant blank 42 h contains two individual blanks for forming theshock towers and so is separated along a line of symmetry 56 intoindividual blanks. Each individual blank is then formed in a press intoa shock tower as shown in FIG. 16 with walls of relatively thin materialbut with mounting plates provided with a double thickness by theconstituent parts 10 h.

The techniques described above may also be utilized to provide a blankincorporating non-weldable components, or components that are notcompatible for welding to one another. For example, mild steel andaluminum are each weldable but when welded to one another brittle,intermetallic compounds are formed.

One such arrangement is shown in FIGS. 18-20 in which a pair ofconstituent parts 10 j,20 j are interconnected by welds 40 j and aremechanically connected to an additional component 60. The component 60is a plastics material and has a series of rectangular depressions 62along marginal edges 64. An undercut 66 is formed on the edge ofconstituent part 10 j with an undersurface 68 spaced from the majorsurface 24 j by the thickness of the additional component 60.Projections 70 depend from the undersurface 68 and are complementary tothe depressions 62 so as to be a snug fit within them.

The constituent parts 10 j,20 j are positioned in juxtaposition with thecomponent 60 is located between. The projections 70 engage thedepressions 62 so that the component 60 is mechanically locked to thepart 10 j. The parts 10 j,20 j are then welded at 40 j to connect themand secure the component 60. The resultant blank may then be formed withthe mechanical connection retaining the integrity of the parts 10 j andcomponent 60. It will be appreciated that the component 60 may be aplastics composite, glass or other material not normally weldable orcould be a dissimilar metal material such as aluminum.

As an alternative to the rectangular depressions 62, part-sphericalrecesses may be used as shown in FIG. 21. In this embodiment, recessesor “dimples” 72 are formed in each of the parts 10 k,20 k and component60 k by a part-spherical punch and the parts 10 k,20 k welded to oneanother to form an integral blank 42 k.

The mechanical interconnection of the component 60 and parts 10,20 maybe utilized in a number of ways as shown in FIG. 22. The component 60may be used to cover an aperture in the part as shown in FIG. 22a,or mayform a lining over a portion of the part 20 as shown in FIG. 22b.

The component 60 may be circular as illustrated in FIG. 22c or may beformed with a peripheral rabett so that a flush surface is provided asshown in FIG. 22d.

In some circumstances, a positive mechanical connection is not necessaryin which case a frictional location is obtained by deflection of one orboth constituent parts as shown in FIGS. 22e-22 h. In such arrangements,the component 60 is mechanically trapped by the constituent parts topermit subsequent forming operations.

It will be seen that the preparation of a tailored blank withconstituent parts juxtaposed permits the blank to be formed withdifferent material characteristics without the need for precision edgepreparation of the parts.

Other typical applications in which the above embodiments find utilityare the provision of a strengthening section in a door skin of a vehicleto receive a door lock assembly or mounting pads for attachment of seatbelts on a floor pan of a vehicle.

Although laser welding is preferred, alternative welding techniques maybe used such as MASH welding that permits the blank to be assembled andsubsequently formed. The welding pattern will be selected to meet thestructural requirements of the forming process, including the drawingproperties of the blank and the components' subsequent use.

By securing the constituent parts into a blank prior to forming, theneed for accurately fitting the parts for seam welding into a unitaryblank is mitigated. Moreover, because the required materialcharacteristics can be obtained from the blank, the need to weldadditional components after the forming process is avoided. This isparticularly significant as the accurate fitting of complex shapes afterforming is difficult and time-consuming. A uniform closed surface mayalso be obtained without relying upon the integrity of the weld.

In each of the above embodiments, a continuous weld has been illustratedbetween the constituent parts. Where structural requirements permit, itis of course possible to provide localized welding at discrete locationsover the constituent parts so that the constituent parts are heldtogether during forming but a continuous weld is not necessary.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A tailored blank forsubsequent forming into a finished component, said blank having a pairof sheet metal constituent parts, each being of substantially uniformthickness, each having a pair of oppositely directed planar majorsurfaces with a major surface of one constituent part juxtaposed with amajor surface of another constituent part, one of said constituent partshaving a peripheral edge within said major surface of said other andsaid constituent parts being welded to one another by a continuous weldseam formed by laser welding extending around said peripheral edge toprovide a unitary blank.
 2. A tailored blank according to claim 1wherein another major surface of one of said constituent parts providesa continuous outwardly directed surface to said blank.
 3. A tailoredblank according to claim 1 wherein said laser welded seam partiallypenetrates said other component and terminates prior to the majorsurface of said other constituent.
 4. A tailored blank of according toany one of claim 1 wherein an aperture is provided in one of saidconstituent part and said other constituent part overlies said aperture.5. A tailored blank for subsequent forming into a finished component,said blank having a pair of metal constituent parts, each having a pairof oppositely directed major surfaces with a major surface of oneconstituent part juxtaposed with a major surface of another constituentpart and having a peripheral edge lying within said major surface ofsaid other constituent part, an intermediate layer interposed betweensaid major surfaces of said constituent parts and lying within saidperipheral edge to provide a peripheral margin, said constituent partsbeing secured to one another by a continuous laser weld located in saidperipheral margin to retain said intermediate layer in situ duringforming.
 6. A tailored blank according to claim 5 wherein saidconstituent parts are seam welded to one another.
 7. A tailored blankaccording to claim 5 wherein said intermediate layer is a non-metal. 8.A method of forming a finished component from constituent parts ofsubstantially uniform thickness of a metal blank, said method comprisingthe steps of forming one of said constituent parts with a peripheraledge lying within a major surface of another of said constituent parts,juxtaposing oppositely directed major surfaces of said constituentparts, directing a laser beam at said peripheral edge to melt it andadjacent portions of said major surface of said other portion to providea continuous laser weld between said constituent parts to one another toprovide a tailored blank having varying physical characteristics andsubsequently forming said tailored blank to provide a finished shapedcomponent.
 9. A method according to claim 8 including the step offorming an aperture in one of said constituent parts prior tojuxtaposition of said parts.
 10. A method according to claim 9 whereinanother of said constituent part is positioned to overlie said apertureprior to welding.
 11. A method according to claim 10 wherein localizeddepression is formed in one of said constituent parts; to receive theother of said constituent parts.
 12. A method according to any one ofclaim 8 wherein said laser welding partially penetrates said otherconstituent part to terminate prior to the other major surface of saidother constituent part.
 13. A method of forming a tubular component froma pair of tubular constituent parts comprising the steps of assemblingsaid tubular parts by locating one intermediate the ends of another toprovide a local internal reinforcement, securing said parts to oneanother via a continuous laser weld, locating said interconnected partsin a die and expanding said tubular parts by application of pressurizedfluid to attain the finished form of tubular component.
 14. A methodaccording to claim 13 including the step of locating a plurality ofconstituent parts intermediate the ends of said other constituent partto provide spaced local reinforcements.
 15. A tailored blank forsubsequent forming into a finished form of tubular component, said blankhaving a pair of tubular metal constituent parts, each being ofsubstantially uniform thickness, each having a pair of oppositelydirected major surfaces with a major surface of one tubular constituentpart located intermediate the ends of a major surface of the othertubular constituent part to provide a local internal reinforcement, andsaid tubular constituent parts being welded to one another by acontinuous weld seam formed by laser welding extending around the endsof said one tubular constituent part to provide a unitary blank.
 16. Atailored blank according to claim 15 wherein another major surface ofone of said constituent parts provides a continuous outwardly directedsurface to said blank.
 17. A tailored blank according to claim 15wherein said laser welded seam partially penetrates said other componentand terminates prior to the other major surface of said otherconstituent.
 18. A tailored blank according to claim 15 wherein anaperture is provided in one of said constituent parts and said otherconstituent part overlies said aperture.
 19. A tailored blank forsubsequent forming into a finished form of tubular component, said blankhaving a pair of tubular metal constituent parts, each being ofsubstantially uniform thickness, each having a pair of oppositelydirected major surfaces with a major surface of one tubular constituentpart located intermediate the ends of a major surface of the othertubular constituent part to provide local internal reinforcement, anintermediate layer interposed between said major surfaces of saidtubular constituent parts and lying within the ends of said innertubular constituent part to provide an end margin, said tubularconstituent parts being welded to one another by a continuous weld seamformed by laser welding extending around the ends of said one tubularconstituent part to retain said intermediate layer in situ duringforming.
 20. A tailored blank according to claim 19 wherein saidconstituent parts are seam welded to one another.
 21. A tailored blankaccording to claim 19 wherein said intermediate layer is a non-metal.